From charging demand to congestion risk in multi-sector transport electrification

Introduction: The rapid electrification of road transport introduces large and stochastic electricity loads that may significantly affect the availability of grid capacity. This study evaluates the combined grid capacity impacts of fully electrified passenger car, long-haul truck, and heavy equipment fleets. Materials and methods: A geographically explicit probabilistic load flow framework is developed to assess the grid impact of large-scale transport electrification. The framework is applied to a real 135 kV sub-transmission network comprising 86 primary substations. The simulation is driven by empirical charging, transport, and operational datasets, including data from approximately 14,000 heavy machinery units. The stochastic charging demand is modeled for fully electrified fleets and spatially aggregated at primary substations. Results: The results show that increases in aggregated charging demand do not translate linearly into sub-transmission congestion risk. While the transition from the lowest-impact to highest-impact charging scenario combination increases aggregated peak charging demand by 33%, the resulting transformer loading is strongly influenced by interactions with background consumption, local grid conditions, and cross-sector temporal diversity. Despite the large increase in electricity demand, only 10 of the 86 studied primary substations exhibited a non-zero overload risk where none was present before, indicating substantial hosting capacity within the studied sub-transmission network. Conclusions: The findings demonstrate the importance of coupling transport electrification models with realistic power system simulations when assessing future grid reinforcement needs. Importantly, charging demand alone provides a poor indicator of actual congestion risk. Furthermore, the effects of the different modeled vehicle fleets do not add proportionally, indicating that the interactions between different vehicle fleets need to be taken into consideration when investigating the grid impact of electrified vehicle fleets.